TimeBell is certainly a great tool. But I already have the perfect solution for all my needs since more than a decade now. It's the freeware UK's Kalender. Small in size and memory footprint (3 MB RAM) it offers all the bells and whistles you could imagine from a calendar/reminder. It comes with 13 languages.http://www.ukrebs-software.de/english/kalender/kalender.html

I tried creating a task, and it reminded me of the task on two different time i had created it. Its pretty good, but the only bad thing i found out was once the task or the reminder was displayed the program deletes the note and there is no other way to recover it (But you could create a backup of the note or the task that has been fed before, pretty robust.). Besides that it looks kind of a ugly and plain, but does the work, that's what i look for in any software.
Although i like it, only time will tell how long i'll use it.
Thank you.

Hello everybody! I would need a similar program like this but with a VERY small memory footprint. The only feature I would need would be a pop-up window with a definable text, that opens up at a certain date/time. Nothing more. Anyone can recommend something to me? Thanks!

M. H., I use an excellent free program called Free Countdown Timer. Very small footprint; allows recurring event; you can customize text and alarm sounds. You can have it boot on startup or not, display floating windows or not, and I haven't found any limit to the number of reminders you can set. Have used it for years and couldn't function without it.